My current Genesis block seems to be just fine - no issues and it made 752HP at 6300 RPM at the Engine Masters deal on 91 octane. Same engine got shipped over to Kaase's for photos and it went 759HP on Jon's dyno...
The aftermarket blocks are all referenced to go to 4.25 bore. The reason is not pistons - - the guys at Diamond will make me any piston I can dream of. We've done some for FEs with blowers, and some for 300 ci inline sixes with turbos... The forgings are FE specific and not converted GM anything.
The reason is piston ring availability. Since the original moter was the only one using that 4.233 bore, standard size rings have become virtually non-existant. Chevrolet size based 4.250 rings are inexpensive and plentiful.
I cannot imagine a reason not to go "big" - but I suppose we could tweak a 391 truck forged crank offset in the "wrong direction" to put the cubes back at 427 with the slight overbore. Wierd but possible. I'd go big if it was mine.
Wait a minute - - I'm doing something a lot like that for next year's Engine Masters Challenge - - taking my 4.350 bore motor and destroking it to meet the 434 cube rules ... I guess the wierd label fits
